1. FIELD OF THE INVENTION
The present invention relates to an electric contact piece intended to be plugged into a bore in an electric circuit plate and having a plug-in section of a substantially U-shaped cross-section which section is elastically yieldable laterally relative to the plug-in direction and includes two elastically bendable legs and a web interconnecting the legs. The invention relates further to a method of producing such a contact piece and to a molding tool for carrying out this method.
2. DESCRIPTION OF THE PRIOR ART
It oftentimes is necessary to connect individual conductors of an electric circuit plate to external electrical circuit components or circuit systems, i.e. such which do not belong to the respective circuit plate or board. To this end electrical contact pieces are known which are plugged into a respective bore in the circuit plate and accordingly can be mechanically mounted to the circuit plate. It is further known to provide the circumferential walls of the bores of the circuit plate which receive the contact pieces with an individual electrically conductive coating, specifically of copper including a tin plating, which coating is in connection with at least one of the conductors of the plate such that upon the plugging-in of each contact piece automatically an impeccable electrical connection between the contact piece and at least one allocated conductor of the plate is made and soldering will thus no longer be necessary.
Numerous shapes of contact pieces are already know for the plugging-in technique described. As a rule such contact pieces have the form of a pin which has a broadened plug-in section having elastically yielding properties in a direction laterally to the longitudinal axis of the pin such that a good fit of the contact piece which has been plugged-in is guaranteed when the inside diameter of the bore in the electrical circuit plate varies within prescribed tolerances.
Until now the broadened plug-in section of the contact pieces has been produced by a local splitting into two legs extending substantially parallel and spread from each other or laterally offset to each other whereto a punching or cutting technique has been used which as a rule led to sharp longitudinal edges of the plug-in section. Such sharp longitudinal edges are burdened with the drawback that during the plugging or pressing in of the contact piece they possibly may cut fine shavings out of the metallic coating on the inner circumferential wall of the bore in the circuit plate which possibly remain adhering someplace on the circuit board and may form disturbing contact bridges between conductors. In order to avoid this danger the outer longitudinal edges of the plug-in section which come into contact with the circumferential wall with the bore in the circuit plate have also been rounded whereby an additional production step during the manufacturing procedure has been necessary.
Several known contact pieces of the kind described have the further drawback that their plug-in section abuts or contacts in the plugged-in operational condition the circumferential wall of the respective bore of the circuit plate at only two outer longitudinal edges which are located roughly diametrically to each other and, therefore, does not in every case sit sufficiently stably and untiltable in the bore. Contact pieces of the kind described are disclosed e.g. in the U.S. Pat. No. 4,186,982 and in the Belgian Patent Specification BE-PS 818,173.
It is, furthermore, known to shape the plug-in section of the contact pieces by a flattening thereof by means of a pressing procedure and thereafter following rolling such that it is given a roughly horseshoe shaped, W-shaped or clover-like cross-section such as e.g. disclosed in the U.S. Pat No. 3,783,433. Such designs demand relatively complicated multistep manufacturing methods.